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Abstract:

Disclosed herein is a composition comprising a graft block copolymer
comprising a first block polymer; the first block polymer comprising a
backbone polymer and a first graft polymer; where the first graft polymer
comprises a surface energy reducing moiety; and a second block polymer;
the second block polymer being covalently bonded to the first block;
wherein the second block comprises the backbone polymer and a second
graft polymer; where the second graft polymer comprises a functional
group that is operative to crosslink the graft block copolymer; a
photoacid generator; and a crosslinking agent.

Claims:

1. A composition comprising: a graft block copolymer comprising: a first
block polymer; the first block polymer comprising a backbone polymer and
a first graft polymer; where the first graft polymer comprises a surface
energy reducing moiety; and a second block polymer; the second block
polymer being covalently bonded to the first block polymer; wherein the
second block polymer comprises the backbone polymer and a second graft
polymer; where the second graft polymer comprises a functional group that
is operative to crosslink the graft block copolymer; a photoacid
generator; and a crosslinking agent.

2. The composition of claim 1, where the backbone polymer is a
polynorbornene.

3. The composition of claim 1, where the first graft polymer is a
poly(fluorostyrene), a poly(tetrafluoro-hydroxy styrene), or a
combination thereof.

4. The composition of claim 1, where the first graft polymer is a
poly(tetrafluoro-para-hydroxy styrene).

5. The composition of claim 1, where the second graft polymer is a
copolymer of a poly(hydroxy styrene) and a poly(N-phenyl maleimide).

6. The composition of claim 5, where a molar ratio of the poly(hydroxy
styrene) to the poly(N-phenyl maleimide) is 1:1.

7. The composition of claim 1, where the photoacid generator comprises a
sulfonium salt and where the crosslinking agent is
N,N,N',N',N'',N''-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-triamine
(HMMM).

8. The composition of claim 1, where the graft block copolymer is used in
amounts of 50 to 80 wt %, the photoacid generator is used in amounts of 5
to 25 wt % and the crosslinking agent is used in amounts of 5 to 25 wt %,
based on the total weight of the composition.

9. A method of manufacturing a photoresist comprising: mixing a
composition comprising: a graft block copolymer comprising: a first block
polymer; the first block polymer comprising a backbone polymer and a
first graft polymer; where the first graft polymer comprises a surface
energy reducing moiety; and a second block polymer; the second block
polymer being covalently bonded to the first block polymer; wherein the
second block polymer comprises the backbone polymer and a second graft
polymer; where the second graft polymer comprises a functional group that
is operative to crosslink the graft block copolymer; a photoacid
generator; and a crosslinking agent; disposing the composition on a
substrate; forming a film on the substrate; disposing a mask on the film;
exposing the film to electromagnetic radiation to form a crosslinked film
that comprises bottle-brushes; baking the film; and dissolving unreacted
portions of the film.

11. The method of claim 9, further comprising using the film as a
photoresist.

12. The method of claim 11, where the photoresist is a negative tone
photoresist.

13. The method of claim 11, where the composition is annealed.

14. The method of claim 11, where the composition further comprises a
solvent.

Description:

BACKGROUND

[0001] This disclosure relates to self-assembled structures, methods of
manufacture thereof and to articles comprising the same.

[0002] Block copolymers form self-assembled nanostructures in order to
reduce the free energy of the system. Nanostructures are those having
average largest widths or thicknesses of less than 100 nanometers (nm).
This self-assembly produces periodic structures as a result of the
reduction in free energy. The periodic structures can be in the form of
domains, lamellae or cylinders. Because of these structures, thin films
of block copolymers provide spatial chemical contrast at the
nanometer-scale and, therefore, they have been used as an alternative
low-cost nano-patterning material for generating nanoscale structures.
While these block copolymer films can provide contrast at the nanometer
scale, it is often difficult to produce copolymer films that can display
periodicity at less than 60 nm. Modern electronic devices however often
utilize structures that have a periodicity of less than 60 nm and it is
therefore desirable to produce copolymers that can easily display
structures that have average largest widths or thicknesses of less than
60 nm, while at the same time displaying a periodicity of less than 60
nm.

[0003] Many attempts have been made to develop copolymers that have
average largest widths or thicknesses of less than 60 nm, while at the
same time displaying a periodicity of less than 60 nm. The assembly of
polymer chains into a regular array, and especially a periodic array, is
sometimes referred to as "bottom up lithography". The processes for
forming periodic structures for electronic devices from block copolymers
within lithography are known as "directed self-assembly". However, four
of the challenges and indeed greatest difficulties in trying to build a
workable electronic device from a periodic array have to do with firstly
the need to register or align that periodic array with great precision
and accuracy to the underlying elements of the circuit pattern, and
secondly the need to form non-periodic shapes in the pattern as part of
the electronic circuit design, and thirdly the ability for the pattern to
form sharp bends and corners and line ends as part of the circuit design
pattern layout requirements, and fourthly the ability for the pattern to
be formed in a multitude of periodicities. These limitations with
bottom-up lithography using periodic patterns formed from block
copolymers have resulted in the need to design complex chemoepitaxy or
graphoepitaxy process schemes for alignment, pattern formation and defect
reduction.

[0004] Conventional `top down` lithography, which creates patterns through
projection and focusing of light or energetic particles through a mask
onto a thin photoresist layer on a substrate, or in the case of electron
beam lithography may involve projection of electrons through an
electromagnetic field in a patternwise manner onto a thin photoresist
layer on a substrate, has the advantage of being more amenable to
conventional methods of alignment of the pattern formation to the
underlaying elements of the circuit pattern, and being able to form
non-periodic shapes in the pattern as part of the circuit design, being
able to directly form line ends and sharp bends, and the ability to form
patterns in a multiplicity of periodicities. However, top down
lithography, in the case of optical lithography, is constrained in the
smallest pattern it can form, as a result of the diffraction of light
through mask openings whose dimension is similar or smaller than the
wavelength, which causes loss of light intensity modulation between the
masked and unmasked regions. Other important factors which limit
resolution are light flare, reflection issues from various film
interfaces, imperfections in the optical quality of the lens elements,
focal depth variations, photon and photoacid shot noise and line edge
roughness. In the case of electron beam lithography, the smallest useful
pattern sizes which can be formed are limited by the beam spot size, the
ability to stitch or merge writing patterns effectively and accurately,
electron scatter and backscatter in the photoresist and underlying
substrates, electron and photoacid shot noise and line edge roughness.
Electron beam lithography is also highly limited by throughput, since the
images are patternwise formed pixel-by-pixel, because as smaller pixel
dimensions are required for smaller pattern sizes, the number of imaging
pixels per unit area increases as the square of the pixel unit dimension.

SUMMARY

[0005] Disclosed herein too is a composition comprising a graft block
copolymer comprising a first block polymer; the first block polymer
comprising a backbone polymer and a first graft polymer; where the first
graft polymer comprises a surface energy reducing moiety; and a second
block polymer; the second block polymer being covalently bonded to the
first block; wherein the second block comprises the backbone polymer and
a second graft polymer; where the second graft polymer comprises a
functional group that is operative to crosslink the graft block
copolymer; a photoacid generator; and a crosslinking agent.

[0006] Disclosed herein too is a method of manufacturing a photoresist
comprising mixing a composition comprising a graft block copolymer
comprising a first block polymer; the first block polymer comprising a
backbone polymer and a first graft polymer; where the first graft polymer
comprises a surface energy reducing moiety; and a second block polymer;
the second block polymer being covalently bonded to the first block;
wherein the second block comprises the backbone polymer and a second
graft polymer; where the second graft polymer comprises a functional
group that is operative to crosslink the graft block copolymer; a
photoacid generator; and a crosslinking agent; disposing the composition
on a substrate; forming a film on the substrate; disposing a mask on the
film; exposing the film to electromagnetic radiation to form a
crosslinked film that comprises bottle-brushes; baking the film; and
dissolving unreacted portions of the film.

BRIEF DESCRIPTION OF THE FIGURES

[0007] FIG. 1 is a schematic depiction of an exemplary brush polymer that
is disposed upon a substrate;

[0008] FIGS. 2A and 2B is a schematic depiction of an exemplary ordering
that occurs when the brush polymer having a surface energy reducing
moiety is disposed upon a substrate;

[0009] FIG. 3 is a photomicrograph showing atomic force microscopy (AFM)
results where the upper images show tapping mode AFM and the lower images
are phase images for (A) the brush control composition (B) brush I and
(C) brush II; and

[0011] As used herein, "phase-separate" refers to the propensity of the
blocks of block copolymers to form discrete microphase-separated domains,
also referred to as "microdomains" or "nanodomains" and also simply as
"domains". The blocks of the same monomer aggregate to form periodic
domains, and the spacing and morphology of domains depends on the
interaction, size, and volume fraction among different blocks in the
block copolymer. Domains of block copolymers can form during application,
such as during a spin-casting step, during a heating step, or can be
tuned by an annealing step. "Heating", also referred to herein as
"baking" or "annealing", is a general process wherein the temperature of
the substrate and coated layers thereon is raised above ambient
temperature. "Annealing" can include thermal annealing, thermal gradient
annealing, solvent vapor annealing, or other annealing methods. Thermal
annealing, sometimes referred to as "thermal curing" can be a specific
baking process for fixing patterns and removing defects in the layer of
the block copolymer assembly, and generally involves heating at elevated
temperature (e.g., 150° C. to 350° C.), for a prolonged
period of time (e.g., several minutes to several days) at or near the end
of the film-forming process. Annealing, when performed, is used to reduce
or remove defects in the layer (referred to as a "film" hereinafter) of
microphase-separated domains.

[0012] The self-assembling layer comprises a block copolymer having at
least a first block and a second block that forms domains through phase
separation that orient perpendicular to the substrate upon annealing.
"Domain", as used herein, means a compact crystalline, semi-crystalline,
or amorphous region formed by corresponding blocks of the block
copolymer, where these regions may be lamellar or cylindrical and are
formed orthogonal or perpendicular to the plane of the surface of the
substrate and/or to the plane of a surface modification layer disposed on
the substrate. In an embodiment, the domains may have an average largest
dimension of 1 to 30 nanometers (nm), specifically 5 to 22 nm, and still
more specifically 5 to 20 nm.

[0013] The term "Mn" used herein and in the appended claims in
reference to a block copolymer of the present invention is the number
average molecular weight of the block copolymer (in g/mol) determined
according to the method used herein in the Examples. The term "Mw"
used herein and in the appended claims in reference to a block copolymer
of the present invention is the weight average molecular weight of the
block copolymer (in g/mol) determined according to the method used herein
in the Examples.

[0014] The term "PDI" or "" used herein and in the appended claims in
reference to a block copolymer of the present invention is the
polydispersity (also called polydispersity index or simply "dispersity")
of the block copolymer determined according to the following equation:

PDI = M W M n . ##EQU00001##

[0015] The transition term "comprising" is inclusive of the transition
terms "consisting of" and "consisting essentially of". The term "and/or"
is used herein to mean both "and" as well as "or". For example, "A and/or
B" is construed to mean A, B or A and B.

[0016] Disclosed herein is a graft block copolymer that comprises a
polymer as its backbone (hereinafter the backbone polymer) with a first
polymer that is grafted onto the backbone polymer. The first polymer
comprises a surface energy reducing moiety that comprises either
fluorine, silicon or a combination of fluorine and silicon. The second
polymer also comprises a functional group that is used to crosslink the
graft block copolymer after it is disposed upon a substrate. Each of the
backbone and the graft polymers can be a homopolymer or a copolymer. The
graft block copolymer can self-assemble in the form of a plurality of
bottle-brushes when disposed upon a substrate. The graft block copolymer
can then be crosslinked to form a film. Upon crosslinking, the film
comprises crosslinked bottle-brushes. The polymer backbone is
topologically similar to the handle of a bottle-brush, while the polymer
grafts emanate radially outwards from the graft block copolymer backbone
to form a structure that is similar to the bristles of the bottle-brush,
hence the use of the term "bottle-brush".

[0017] Disclosed herein too is a graft block copolymer that comprises a
plurality of block copolymers each of which comprise the backbone polymer
and where the first polymer and a second polymer are grafted onto the
backbone. The backbone polymer may be a homopolymer or a block copolymer.
The first polymer and the second polymer can be homopolymers or
copolymers. In an exemplary embodiment, the first polymer is a
homopolymer that comprises a surface energy reducing moiety, while the
second polymer is a copolymer that has a functional group through which
the graft block copolymer is crosslinked.

[0018] When the graft block copolymer is disposed upon a substrate it
forms a film that comprises bottle-brush polymers that are then
crosslinked together by reacting the functional groups.

[0019] In one embodiment, the graft block copolymer comprises a first
block polymer and a second block polymer. The first block polymer thus
comprises the backbone polymer with the first polymer (a homopolymer)
grafted onto the backbone polymer. The first polymer is also referred to
herein as the first graft polymer. The second block polymer comprises the
backbone polymer with the second polymer (a copolymer) grafted onto the
backbone polymer. The second polymer is also referred to herein as the
second graft polymer. The first graft polymer and the second graft
polymer are also referred to as flexible polymers. The first block
polymer is therefore a copolymer while the second block polymer is a
terpolymer. The first polymer and/or the second polymer comprises a
functional group that is used to crosslink the graft block copolymer. In
one embodiment, the graft block copolymer is crosslinked after it is
disposed upon a substrate.

[0020] The first polymer comprises the surface energy reducing moiety that
drives higher degrees of self-assembly when the graft block copolymer is
disposed upon a substrate. The presence of the surface energy reducing
moiety results in domain sizes and inter domain periodic spacing that are
less than 30 nanometers, preferably less than 20 nanometers, and more
preferably less than 15 nanometers, when the copolymer is disposed upon a
substrate. These narrow domain sizes and narrow interdomain spacings are
very useful for lithography. They can be used to produce semiconductors
and other electronic components. In one embodiment, the graft block
copolymer can be crosslinked and then used as a negative tone
photoresist. In another embodiment, the graft block copolymer is not
crosslinked and is used as a positive tone photoresist.

[0021] Disclosed herein too is a method of manufacturing the graft block
copolymer. The method comprises producing a series of macromonomers (that
form the backbone polymer) and then performing sequential
grafting-through polymerizations to create the graft copolymer.
Alternatively, grafting-onto or grafting-from techniques can be used for
the graft copolymer syntheses.

[0022] Disclosed herein too is a photoresist composition that comprises
the graft block copolymer, a photoacid generator and a crosslinker. The
photoresist composition is manufactured by crosslinking the photoresist
composition that comprises bottle-brush polymers that have both the
surface energy reducing and reactive moieties. Disclosed herein too are
articles that comprise the graft block copolymer. In one embodiment, the
article comprises a photoresist.

[0023] FIG. 1 depicts a polymeric graft block copolymer 200 (having a
bottle brush morphology) that comprises a polymer backbone 202
(hereinafter the "backbone polymer") of length "l" that is reacted to the
graft polymer 204 (hereinafter the "first graft polymer)". The first
graft polymer can be covalently reacted to the polymer backbone along a
portion of the length of the backbone or along the entire length of the
backbone. The first polymer can also be covalently bonded to the backbone
polymer backbone 202 along the entire length of the backbone and could
extend radially outward in any direction or combination of directions
from the backbone or along a portion of the circumference of the
backbone. In our nomenclature, bottle-brush polymers are different from
polymer brushes in that in a polymer brush, the graft polymer is reacted
to only one surface of a substrate, while in a bottle brush polymer, the
graft polymer is grafted on all sides of the polymer backbone, thus
producing a morphology that appears to be bottle-brush like in
appearance. Polymer brushes are analogous in morphology to a field of
grass, where the polymer is the grass and is disposed on a substrate
(which is analogous to the soil in which the grass grows).

[0024] In one embodiment, the graft block copolymers 200 self-assemble
(upon being disposed upon a surface) such that the resulting assembly
displays order in at least one direction, specifically at least in two
directions, and more specifically at least in three directions. In one
embodiment, the graft block copolymer bottle-brushes self-assemble (upon
being disposed upon a surface) such that the resulting assembly displays
order in at least two mutually perpendicular directions, and more
specifically in at least three mutually perpendicular directions. The
term "order" refers to periodicity between repeating structures in the
assembly when measured in a particular direction.

[0025] The backbone polymer is generally used to form the polymer backbone
202 of the graft block copolymer. It is desirable for the backbone
polymer that forms the backbone to allow for sequential polymerization of
macromonomers to manufacture the graft block copolymers. In one
embodiment, the backbone polymer can be one that comprises a strained
ring along the chain backbone. In another embodiment, the backbone
polymer can be a polyacetal, a polyacrylic, a polycarbonate, a
polystyrene, a polyester, a polyamide, a polyamideimide, a polyarylate, a
polyarylsulfone, a polyethersulfone, a polyphenylene sulfide, a polyvinyl
chloride, a polysulfone, a polyimide, a polyetherimide, a
polytetrafluoroethylene, a polyetherketone, a polyether etherketone, a
polyether ketone ketone, a polybenzoxazole, a polyoxadiazole, a
polybenzothiazinophenothiazine, a polybenzothiazole, a
polypyrazinoquinoxaline, a polypyromellitimide, a polyquinoxaline, a
polybenzimidazole, a polyoxindole, a polyoxoisoindoline, a
polydioxoisoindoline, a polytriazine, a polypyridazine, a polypiperazine,
a polypyridine, a polypiperidine, a polytriazole, a polypyrazole, a
polypyrrolidine, a polycarborane, a polyoxabicyclononane, a
polydibenzofuran, a polyphthalide, a polyanhydride, a polyvinyl ether, a
polyvinyl thioether, a polyvinyl alcohol, a polyvinyl ketone, a polyvinyl
halide, a polyvinyl nitrile, a polyvinyl ester, a polysulfonate, a
polynorbornene, a polysulfide, a polythioester, a polysulfonamide, a
polyurea, a polyphosphazene, a polysilazane, a polyurethane, or the like,
or a combination including at least one of the foregoing polymers. In an
exemplary embodiment, the backbone polymer is polynorbornene. The ring of
the polynorbornene repeat units may, if desired, be substituted with an
alkyl group, an araalkyl group, or an aryl group.

[0026] The number of repeat units in the backbone polymer (that forms the
backbone of the copolymer) is about 3 to about 75, specifically about 10
to about 60, specifically about 25 to about 45. The number average
molecular weight of the backbone is 200 to 10,000 grams per mole as
measured by GPC. In a preferred embodiment, the number average molecular
weight of the backbone is 3,050 to 5,500 grams per mole as measured by
GPC.

[0027] The backbone polymer (that forms the polymer backbone) has grafted
onto it the first polymer thereby forming a graft copolymer. In one
embodiment, the backbone polymer has grafted onto it one or more
different types of graft polymers. In another embodiment, the backbone
polymer has grafted onto it two or more different types of graft
polymers. The graft block copolymer can thus be a block copolymer, an
alternating copolymer, an alternating block copolymer, a random
copolymer, a random block copolymer, or a combination thereof.

[0028] In one embodiment, the graft block copolymer can comprise the
backbone polymer with a first polymer that is grafted onto the backbone
polymer. The first polymer is preferably a homopolymer and comprises the
surface energy reducing moiety. The surface energy reducing moieties
generally comprise silicon atoms, fluorine atoms, or a combination of
fluorine atoms and silicon atoms. The surface energy reducing moiety
facilitates a high degree of self-assembly when the graft block copolymer
is disposed upon a substrate. The first polymer may be covalently or
ionically bonded onto the backbone polymer. In an exemplary embodiment,
the first polymer is covalently bonded onto the backbone polymer.

[0029] In one embodiment, the first polymer is a poly(fluorostyrene)
having 1 to 5 fluorine substituents on the styrenic moiety, a
poly(fluoro-hydroxy styrene), where the styrenic moiety can have 1 to 4
hydroxyl substituents and 1 to 4 fluorine substituents and where the
location of the hydroxyl substituents and the fluorine substituents are
independent of each other, a poly(tetrafluoro-para-hydroxy styrene), or a
copolymer thereof. In an exemplary embodiment, the first polymer is a
poly(tetrafluoro-para-hydroxy styrene). Exemplary first polymers are a
poly(fluorostyrene), a poly(tetrafluoro-hydroxy styrene), or a
combination comprising at least one of the foregoing first polymers.

[0030] In one embodiment, it is desirable for the first polymer (e.g., the
poly(fluorostyrene)) to have a water contact angle of 70 to 90 degrees.
In an exemplary embodiment, it is desirable for the first polymer to have
a preferred water contact angle of 85 to 90 degrees. The first polymer
generally has a number of repeat units of 5 to 20, preferably 7 to 16,
and more specifically 8 to 14. In one embodiment, the first polymer has a
number average molecular weight of 1350 to 6000 Daltons when measured
using gel permeation chromatography (GPC). The first polymer has a PDI of
1.05 to 1.20, specifically 1.08 to 1.12 as determined by GPC.

[0031] In an exemplary embodiment, the first block polymer of the graft
block copolymer comprises a polynorbornene backbone polymer to which is
grafted the first polymer that comprises a poly(tetrafluoro-para-hydroxy
styrene) and has the structure in the formula (1) below:

##STR00001##

where n is 5 to 20 and q is 3 to 75.

[0032] As detailed above, the graft block copolymer can also comprise a
second polymer that is grafted onto the backbone polymer in addition to
the first polymer. The first polymer is the homopolymer detailed above,
while the second polymer is a copolymer. In one embodiment, the second
polymer does not contain a surface energy reducing moiety that comprises
silicon, fluorine, or a combination of silicon or fluorine. In another
embodiment, the second polymer contains the surface energy reducing
moiety that comprises silicon, fluorine, or a combination of silicon or
fluorine, but has a different chemical structure from the first polymer.
The second polymer may also contain a functional group that contains a
functional group that facilitates crosslinking of the graft block
copolymer.

[0033] In one embodiment, the second polymer is a poly(hydroxy styrene), a
poly(N-phenyl maleimide), or a copolymer thereof. In another embodiment,
the poly(hydroxy styrene) is a poly(para-hydroxy styrene). In an
exemplary embodiment, the second polymer is a copolymer of poly(hydroxy
styrene) and poly(N-phenyl maleimide) denoted by poly(para-hydroxy
styrene-co-N-phenyl maleimide). When the second polymer is a copolymer of
poly(hydroxy styrene) and poly(N-phenyl maleimide) denoted by
poly(para-hydroxy styrene-co-N-phenyl maleimide), the poly(hydroxy
styrene), the molar ratio of poly(N-phenyl maleimide) to
poly(para-hydroxy styrene-co-N-phenyl maleimide) is 1:6 to 6:1,
specifically 1:3 to 3:1, and more specifically 1:2 to 2:1. In an
exemplary embodiment, the molar ratio of poly(N-phenyl maleimide) to
poly(para-hydroxy styrene-co-N-phenyl maleimide) in the second polymer is
1:1.

[0034] In one embodiment, it is desirable for the second polymer (e.g.,
the copolymer of polyhydroxystyrene and poly(N-phenylene maleimide) and
to have a contact angle of 15 to 80 degrees, when contacted with water.
In an exemplary embodiment, it is desirable for the second polymer to
have a preferred water contact angle of 45 to 65 degrees. The second
polymer generally has a number of repeat units of 6 to 95, preferably 12
to 30, and more preferably 14 to 28 when measured using gel permeation
chromatography (GPC). In one embodiment, the second polymer has a number
average molecular weight of 1850 to 6250 Daltons when measured using GPC.
The second polymer has a PDI of 1.05 to 1.30, preferably 1.05 to 1.15 as
determined by GPC.

[0035] In another exemplary embodiment, the second block graft comprises a
polynorbornene backbone to which is grafted the second polymer that
comprises poly(para-hydroxy styrene-co-N-phenyl maleimide) and has the
structure in the formula (2) below:

##STR00002##

where m is 10 to 40, x is 0.25 to 1.5, y is 0.25 to 1.5 and p is 3 to 75.

[0036] The first block polymer is reacted with the second block polymer to
produce the graft block copolymer having the structure of the formula (3)
below:

##STR00003##

where m, n, p, q, x and y are specified above.

[0037] The copolymer can be manufactured in a batch process or in a
continuous process. The batch process or the continuous process can
involve a single or multiple reactors, single or multiple solvent and
single or multiple catalysts (also termed initiators).

[0038] In one embodiment, in one method of producing the graft block
copolymer, the first block polymer is synthesized separately from the
second block polymer. The first block polymer is reactively bonded to the
second block polymer to form the graft block copolymer.

[0039] The first block is manufactured by reacting a precursor to the
backbone polymer with a chain transfer agent to form backbone polymer
precursor-chain transfer agent moiety in a first reactor. The backbone
polymer precursor-chain transfer agent moiety is then reacted with a
precursor to the first polymer to form the first polymer using reversible
addition-fragmentation chain transfer (RAFT) polymerization. The first
polymer is covalently bonded to the precursor of the backbone polymer
during the RAFT polymerization, which is conducted in the first reactor
in the presence of a first solvent and a first initiator. The precursor
to the backbone polymer is then polymerized via ring opening metathesis
polymerization (ROMP) to form the first block polymer. The ROMP reaction
may be conducted in the first reactor or in another reactor. The first
block polymer comprises the backbone polymer with the first polymer
grafted onto it. This first block polymer may be disposed upon a
substrate to produce a self-assembled film without copolymerizing it to
the second block. The film can then be crosslinked using radiation.

[0040] The second block polymer may be polymerized in a second reactor if
desired. A precursor to the backbone polymer is reacted with a chain
transfer agent to form a backbone polymer precursor-chain transfer agent
moiety. The backbone polymer precursor-chain transfer agent moiety is
then reacted with the precursor to the second polymer to form the second
polymer using reversible addition-fragmentation chain transfer (RAFT)
polymerization. The second polymer is covalently bonded to the first
polymer precursor-chain transfer agent moiety during the RAFT
polymerization, which is conducted in the presence of a second solvent
and a second initiator. Since the second polymer is a copolymer, there
are two or more precursors that are reacted together with the precursor
to the backbone polymer to form the second graft polymer. The precursor
to the second polymer is then polymerized via a second ring opening
metathesis polymerization (ROMP) to form the second block polymer. The
second block polymer comprises the backbone polymer with the second
polymer grafted onto it. In the production of the first and the second
block polymers, the first reactor may be the same as the second reactor,
the first solvent may be the same as the second solvent and the first
initiator may be the same as the second initiator. In one embodiment, the
first reactor may be different from the second reactor, the first solvent
may be different from the second solvent and the first initiator may be
different from the second initiator.

[0041] In one embodiment, the first block polymer is reacted with the
second block polymer in a second ring opening metathesis polymerization
to form the graft block copolymer. The second ring opening metathesis
polymerization may be conducted in either the first reactor, the second
reactor or in a third reactor. The graft block copolymer is then purified
by a variety of different methods that are listed below. It may then be
disposed upon a substrate to produce a higher degree of self-assembly
than the self-assembly produced by disposing either the first block
polymer or the second block polymer by themselves on the substrate.

[0042] In an exemplary embodiment, when the backbone polymer is
polynorbornene, when the first polymer is poly(tetrafluoro-para-hydroxy
styrene) and when the second polymer is poly(para-hydroxy
styrene-co-N-phenyl maleimide), the reaction to produce the graft block
copolymer is as follows.

[0043] The first polymer is produced by reacting the norbornene with a
dithioester chain transfer agent to produce a norbornene-chain transfer
agent moiety. The norbornene-chain transfer agent moiety is then reacted
with tetrafluoro-para-hydroxy styrene (TFpHS) monomer in a RAFT reaction
to homopolymerize the tetrafluoro-para-hydroxy styrene to form the
norborne-poly(tetrafluoro-para-hydroxy styrene) homopolymer (i.e., the
first polymer). The reaction is demonstrated in reaction (1) below.

##STR00004##

[0044] In the reaction (1) above, the molar ratio of the norbornene to the
chain transfer agent is 0.5:1 to 1:0.5, preferably 0.75:1 to 1:0.75 and
more preferably 0.9:1 to 1:0.9. In an exemplary embodiment, the molar
ratio of the norbornene to the chain transfer agent is 1:1.

[0045] The molar ratio of the norbornene-chain transfer agent to the
tetrafluoro-para-hydroxy styrene (TFpHS) monomer is 1:10 to 1:100,
preferably 1:15 to 1:50 and more preferably 1:20 to 1:30. In an exemplary
embodiment, the molar ratio of the norbornene-chain transfer agent to the
tetrafluoro-para-hydroxy styrene (TFpHS) is 1:30.

[0046] The reaction (1) above may be conducted in a first solvent.
Suitable solvents for conducting the reaction are polar solvents,
non-polar solvents, or combinations thereof. Examples of solvents are
aprotic polar solvents, polar protic solvents, or non-polar solvents. In
one embodiments, aprotic polar solvents such as propylene carbonate,
ethylene carbonate, butyrolactone, acetonitrile, benzonitrile,
nitromethane, nitrobenzene, sulfolane, dimethylformamide,
N-methylpyrrolidone, 2-butanone, acetone, hexanone, acetylacetone,
benzophenone, acetophenone, or the like, or combinations comprising at
least one of the foregoing solvents may be used. In another embodiment,
polar protic solvents such as water, methanol, acetonitrile,
nitromethane, ethanol, propanol, isopropanol, butanol, or the like, or
combinations comprising at least one of the foregoing polar protic
solvents may also be used. Other non-polar solvents such a benzene,
alkylbenzenes (such as toluene or xylene), methylene chloride, carbon
tetrachloride, hexane, diethyl ether, tetrahydrofuran, 1,4-dioxane, or
the like, or combinations comprising at least one of the foregoing
solvents may also be used. Co-solvents comprising at least one aprotic
polar solvent and at least one non-polar solvent may also be utilized to
modify the swelling power of the solvent and thereby adjust the rate of
reaction. In an exemplary embodiment, the first solvent is 2-butanone. It
is desirable to use anhydrous solvent for conducting the reaction.

[0047] The weight ratio of the solvent to the TFpHS is about 1:1 to about
5:1, specifically about 1.5:1 to about 3:1, and more specifically about
1.6:1 to about 2:1.

[0048] A first initiator may be used to initiate the first RAFT reaction.
Examples of suitable initiators are azobisisobutyronitrile (AIBN),
4,4'-azobis(4-cyanovaleric acid) (ACVA), also called
4,4'-azobis(4-cyanopentanoic acid), di-tert-butyl peroxide (tBuOOtBu),
benzoyl peroxide ((PhCOO)2), methyl ethyl ketone peroxide, tert-amyl
peroxybenzoate, dicetyl peroxydicarbonate, or the like or a combination
comprising at least one of the foregoing initiators. The first initiator
may also be a radical photoinitiator. Examples are benzoyl peroxide,
benzoin ethers, benzoin ketals, hydroxyacetophenone, methylbenzoyl
formate, anthroquinone, triarylsulfonium hexafluorophosphate salts,
triarylsulfonium hexafluoroantimonate salts, phosphine oxide compounds
such as Irgacure 2100 and 2022 (sold by BASF), or the like, or a
combination comprising at least one of the foregoing radical initiators.

[0049] The initiator is used in molar ratio of 0.05 to 0.2 with respect to
the norbornene-chain transfer agent. In an exemplary embodiment, the
initiator is used in molar ratio of 0.07 to 0.18 with respect to the
norbornene-chain transfer agent. The first RAFT reaction between the
norbornene-chain transfer agent and the tetrafluoro-para-hydroxy styrene
to form the first polymer is conducted in the first reactor under
agitation and at a temperature of 50 to 80° C., preferably 60 to
70° C. In an exemplary embodiment, the first RAFT reaction is
conducted at a temperature of 65° C. The first polymer may be
purified after its preparation by precipitation, washing, distillation,
decanting, centrifugation, or the like. In an exemplary embodiment, the
first polymer is purified by precipitation in hexane.

[0050] The second polymer is produced by reacting the norbornene with a
dithioester chain transfer agent to produce a norbornene-chain transfer
agent moiety. The norbornene-chain transfer agent moiety is then reacted
with para-hydroxy styrene (pHS) and N-phenyl maleimide (PhMI) in a second
reactor to produce the second polymer. The reaction is demonstrated in
reaction (2) below.

##STR00005##

[0051] In the reaction (2) above, the molar ratio of the norbornene to the
chain transfer agent is 0.5:1 to 1:0.5, preferably 0.75:1 to 1:0.75 and
more preferably 0.9:1 to 1:0.9. In an exemplary embodiment, the molar
ratio of the norbornene to the chain transfer agent is 1:1. The molar
ratio of para-hydroxy styrene to N-phenyl maleimide is 0.5:1 to 1:0.5,
preferably 0.75:1 to 1:0.75 and more preferably 0.9:1 to 1:0.9. In an
exemplary embodiment, the molar ratio of the para-hydroxy styrene to
N-phenyl maleimide is 1:1. The molar ratio of the norbornene-chain
transfer agent to the para-hydroxy styrene and N-phenyl maleimide is 1:10
to 1:100, preferably 1:15 to 1:50 and more preferably 1:2 to 1:40. In an
exemplary embodiment, the molar ratio of the norbornene-chain transfer
agent to the monomer of para-hydroxy styrene and N-phenyl maleimide is
1:1.

[0052] The reaction (2) above may be conducted in a second solvent. The
solvent may be chosen from the list of solvents mentioned above. The
weight ratio of the solvent to the monomers is about 1:1 to about 10:1,
specifically about 2:1 to about 6:1, and more specifically about 3:1 to
about 4:1. In an exemplary embodiment, the second solvent is anhydrous
1,4-dioxane. An initiator may be used to initiate the second RAFT
reaction. The initiators disclosed above may be used for the second RAFT
reaction.

[0053] The initiator (for the preparation of the second polymer) is used
in molar ratio of 0.05 to 0.2 with respect to the norbornene-chain
transfer agent. In an exemplary embodiment, the initiator is used in
molar ratio of 0.06 to 0.15 with respect to the norbornene-chain transfer
agent.

[0054] The second RAFT reaction between the norbornene-chain transfer
agent and the copolymer of para-hydroxy styrene and N-phenyl maleimide to
form the second polymer is conducted in the first reactor under agitation
and at a temperature of 50 to 80° C., preferably 55 to 75°
C., and more preferably 60 to 65° C. In an exemplary embodiment,
the second RAFT reaction is conducted at a temperature of 65° C.
The second polymer may be purified after its preparation by
precipitation, washing, distillation, decanting, centrifugation, or the
like. In an exemplary embodiment, the second polymer is purified by
precipitation in diethyl ether.

[0055] The first polymer prepared via the reaction (1) and the second
polymer prepared via the reaction (2) are then subjected to the ring
opening metathesis polymerization reaction (3) to convert the norbornene
to polynorbornene and form the graft block copolymer. The reaction may be
conducted in the first reactor, the second reactor or in a third reactor
that is independent from the first two reactors. The reactors should be
cleaned out prior to the reaction. The reaction is conducted in the
presence of a modified Grubbs catalyst. The Grubbs catalyst may be a
first generation Grubbs catalyst, a second generation Grubbs catalyst, a
Hoveyda-Grubbs catalyst, or the like, or a combination comprising at
least one of the foregoing Grubbs catalyst. The Grubbs catalyst may be a
fast initiating catalyst if desired.

[0056] An exemplary modified Grubbs catalyst is shown in formula (4).

##STR00006##

where Mes represents mesitylene or 1,3,5-trimethylbenzene.

[0057] The molar ratio of the Grubbs catalyst to the first polymer is 1:1
to 1:10. In an exemplary embodiment, the molar ratio of the Grubbs
catalyst to the first polymer is 1:4. The molar ratio of the Grubbs
catalyst to the second polymer is 1:1 to 1:100. In an exemplary
embodiment, the molar ratio of the Grubbs catalyst to the second polymer
is 1:30.

[0058] In the reaction (3), the molar ratio of the first polymer to the
second polymer is 1:2 to 1:20. In an exemplary embodiment, in the
reaction (3), the molar ratio of the first polymer to the second polymer
is 1:7.

[0059] In one embodiment, in one method of preparing the graft block
copolymer, the catalyst is first added to the reactor with a solvent and
the mixture is agitated to obtain a homogenous solution. The first
polymer and the second polymer are then sequentially added to the
reactor. The reactor is agitated for a period of 1 to 5 hours. The
polymerization was then quenched with a quencher. The graft block
copolymer is then purified.

##STR00007## ##STR00008##

[0060] As detailed above, the first polymer and/or the second polymer
comprise functional groups that are used for crosslinking the graft block
copolymer. In one embodiment, any aromatic group having an R--OH or an
R--SH functional group may be used for crosslinking the graft block
copolymer. The functional group can be selected from the group consisting
of a phenol, a hydroxyl aromatic, a hydroxyl heteroaromatic, an aryl
thiol, a hydroxyl alkyl, a primary hydroxyl alkyl, a secondary hydroxyl
alkyl, a tertiary hydroxyl alkyl, an alkyl thiol, a hydroxyl alkene, a
melamine, a glycoluril, a benzoguanamine, an epoxy, a urea, or
combinations thereof. An exemplary functional group is an alkyl alcohol,
such as hydroxyl ethyl, or an aryl alcohol, such as phenol. In an
exemplary embodiment, the second polymer comprises the functional group
that can be used for crosslinking the graft block copolymer.

[0061] As noted above, the first polymer, the second polymer and the graft
block copolymer may be purified by a variety of methods. Purification of
the respective polymers is optional. The reactants, the respective
polymers, and the graft block copolymer may be purified prior to and/or
after the reaction. Purification may include washing, filtration,
precipitation, decantation, centrifugation, distillation, or the like, or
a combination comprising at least one of the foregoing methods of
purification.

[0062] In one exemplary embodiment, all reactants including the solvents,
initiators, endcapping agents and quenchers are purified prior to the
reaction. It is generally desirable to use reactants, solvents and
initiators that are purified to an amount of greater than or equal to
about 90.0 wt % purity, specifically greater than or equal to about 95.0
wt % purity and more specifically greater than about or equal to about
99.0 wt % purity. In another exemplary embodiment, after polymerization
of the graft block copolymer, it may be subjected to purification by
methods that include washing, filtration, precipitation, decantation,
centrifugation or distillation. Purification to remove substantially all
metallic impurities and metallic catalyst impurities may also be
conducted. The reduction of impurities reduces ordering defects when the
graft block copolymer is annealed, and reduces defects in integrated
circuits used in electronic devices.

[0064] The graft block copolymer after purification may be used to
manufacture a photoresist composition. The photoresist composition
comprises the graft block copolymer, a solvent, a crosslinking agent, and
a photoacid generator. In one embodiment, the graft block copolymer may
be dissolved in a solvent along with a photo acid generator and a
crosslinking agent and then disposed upon the surface of a substrate to
form a graft block copolymer film that displays order in one or more
directions, preferably in two or more directions and more preferably in
three or more directions. In one embodiment, these directions are
mutually perpendicular to each other.

[0065] The graft block copolymer disposed upon the surface of the
substrate undergoes self-assembly in the form of bottle-brushes on the
surface of the substrate. In one embodiment, when the copolymer comprises
only a single block (i.e., either the first block polymer or the second
block polymer), the brushes may self-assemble in only two dimensions on
the surface of the substrate, i.e., the backbone polymers may not be
oriented with their backbones disposed perpendicular to the surface of
the substrate.

[0066] When the copolymer comprises two blocks (i.e., it is a graft block
copolymer) and when one block copolymer comprises the surface energy
reducing moiety, the brushes self-assemble in such a manner so that the
backbone polymer is oriented substantially perpendicular to the surface
of the substrate, while the first and second polymers extend radially
outwards from the backbone polymer. The first and second polymers are
substantially parallel to the surface of the substrate, when the backbone
polymer is disposed substantially perpendicular to the surface of the
substrate. This morphology is termed the vertical oriented bottle-brush
morphology.

[0067] In one embodiment, when a monolayer of the graft block copolymer is
disposed on a substrate, the individual polymer chains align with their
backbones disposed substantially perpendicular to the substrate and the
graft polymers extend radially outwards from the backbone. When two or
more monolayers are disposed on the substrate, the bottle-brushes of the
second layer may be inter-digitated with the bottle brushes of the first
monolayer.

[0068] In one embodiment, the presence of the fluorine atoms in the
terpolymer promotes the self-assembly of the brushes in three directions.
Since the fluorine atom reduces the surface energy of the terpolymer, it
facilitates an orientation of the terpolymer with the first block (the
block that contains the fluorine atoms) located at the farthest end of
the copolymer from the substrate. The FIGS. 2A and 2B display a top view
and a side view respectively of the terpolymer that contains a polymer
backbone 202, with the first polymer 204 grafted onto the backbone. The
FIG. 2A (which represents the top view) shows that the brushes
self-assemble to display order in two mutually perpendicular directions
(y and z, which are in the plane of the substrate), while the FIG. 2B
(which represents the side view) shows order in the third direction (the
x-direction, which is perpendicular to the plane of the substrate). In
the FIGS. 2A and 2B, the backbone polymer 200 has grafted onto it both
the first polymer 203 (which comprises the surface energy reducing
moiety) and the second polymer 205 (which does not contain a surface
energy reducing moiety) and the presence of the surface energy reducing
moiety produces order in three mutually directions. The order is
reflected by the periodicity of the structures shown in the FIGS. 2A and
2B. The periodicity of the structures could be in either planar ordered
arrays such as square packed or hexagonal close packed (hcp) arrays, or
the packing arrangement can have various degrees of packing disorder.
Compression and extension of the first and second polymers allows for
planar packing of the bottle brush structures to conform and adjust to
the local enthalpic and entropic energetic requirements in the packed
film state. When the terpolymer does not contain the surface energy
reducing moiety (e.g., fluorine atoms), the self-assembly in the
x-direction, which is perpendicular to the plane of the substrate, does
not take place as completely, and thus a number of the terpolymers within
the film often lie flat in the y and z direction.

[0069] The graft block copolymer may be disposed upon the substrate by a
variety of methods such as spray painting, spin casting, dip coating,
brush coating, application with a doctor blade, or the like.

[0070] In one embodiment, a photoresist composition comprising the graft
block copolymer, a crosslinking agent, and a photo acid generator may
first be mixed (blended) and applied to the substrate to form a
self-assembled film. The film is then dried to remove solvents. The
resultant film thickness can be measured by a variety of techniques
including ellipsometry, AFM, and SEM. When the bottle brush terpolymers
are substantially self-assemble in the x-direction, which is
perpendicular to the plane of the substrate, and if the casting solution
is sufficiently dilute and the spin speed is adjusted so that the
substrate if coated with a monolayer of terpolymer chains, the film
thickness will be approximately an the length of the terpolymer backbone.
The film is subjected to radiation to crosslink the terpolymer. A portion
of the film may be protected from the radiation with a mask and this
portion will not undergo any significant crosslinking. The uncrosslinked
portions of the film may then be removed using a solvent or by etching
leaving behind a patterned film. The patterned film may be used as a
photoresist after baking and further developing.

[0071] In one embodiment, a photoresist composition comprising the graft
block copolymer, a crosslinking agent, and a photoacid generator may
first be applied to the substrate to form a self-assembled film. The film
is then dried to remove solvents. The film is subjected to electron beam
radiation to crosslink the terpolymers. A portion of the film may be free
from irradiation by either not directing the electron beam over this
portion of the film, or with a mask. This unirradiated portion will not
undergo any significant crosslinking. The uncrosslinked portions of the
film may then be removed using a solvent or by etching leaving behind a
patterned film. The patterned film may be used as a photoresist after
baking and further developing.

[0072] An exemplary photoacid generator (PAG) is triphenylsulfonium
hexafluoroantimonate and an exemplary crosslinking agent is
N,N,N',N',N'',N''-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-triamine
(HMMM). Other crosslinking agents are methylols, alkoxymethylene ethers,
epoxies, novolacs, melamines, resorcinols, and the like, or a combination
comprising at least one of the foregoing crosslinking agents.

[0073] In the photoresist composition, the copolymer is used in amounts of
50 to 80 wt %, the photoacid generator is used in amounts of 5 to 25 wt %
and the crosslinking agent is used in amounts of 5 to 25 wt %, based on
the total weight of the photoresist composition. The photoresist
composition may contain solvents if desired.

[0074] In one embodiment, the graft block copolymer may be used to
selectively interact, or pin, a domain of the block copolymer that is
disposed upon the graft block copolymer to induce order and registration
of the block copolymer morphology. The graft block copolymer has a
topology that can induce alignment and registration of one or more of the
domains of the block copolymer.

[0075] The graft block copolymer can be used as a template to decorate or
manufacture other surfaces that may be used in fields such as
electronics, semiconductors, and the like. The graft block copolymer has
a number of significant advantages over other block copolymers that can
self-assemble and that are used in the formation of photoresists. By
using graft block copolymers where a high degree of control is exerted
over the synthetic chemistry, large-areas of vertical alignment of the
graft block copolymer are achieved in films having a thickness of less
than 50 nanometers (nm), preferably less than 30 nm, without the need for
supramolecular assembly processes as are required for other comparative
forms of linear block copolymer lithography. The structural and
morphological features of the graft block copolymers can be tuned in the
lateral and longitudinal directions thus enabling the preparation of
high-sensitivity photoresists. Furthermore, the structural and
morphological features of the graft block copolymers can be tuned in the
lateral and longitudinal directions to facilitate an enhanced anisotropic
vertical diffusion of photoacid catalyst. These photoresists (each
comprising only a few graft block copolymers) can be used for
photolithography in conjunction with high energy electromagnetic
radiation (e.g., X-ray, electron beam, neutron beam, ionic radiation,
extreme ultraviolet (having photons with energies from 10 eV up to 124
eV), and the like) with line-width resolutions of less than or equal to
about 30 nm. The high-sensitivity of the graft block copolymer
photoresist further facilitates the generation of latent images without
post-exposure baking, which provides a practical approach for controlling
acid reaction-diffusion processes in photolithography. The graft block
copolymer, the photoresist composition and the photoresists derived
therefrom are detailed in the following non-limiting examples.

Example

[0076] This example is conducted to demonstrate the preparation of the
graft block copolymer. The first block comprises a polynorbornene
backbone polymer to which is grafted the first polymer--a
poly(tetrafluoro-para-hydroxy styrene). The second block comprises a
polynorbornene backbone polymer to which is grafted the second polymer--a
copolymer of poly(para hydroxy styrene) and poly(N-phenyl maleimide).

[0077] The materials used for the production of the graft block copolymer
are as follows:

[0078] The modified Grubbs catalyst, 4-hydroxystyrene (pHS),
2,3,5,6-tetrafluoro-4-hydroxystyrene (TFpHS), and the norbornene-chain
transfer agents (NB-CTA) were synthesized according to the literature
reports provided in the following references:

[0083] The N,N,N',N;N'',N''-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-tr-
iamine (HMMM) was purchased from TCI and used without further
purification. The photoacid generators (PAGs)--triphenylsulfonium
hexafluoroantimonate for photolithography, and triphenylsulfonium
perfluoro-1-butanesulfonate for electron beam lithography (EBL),
respectively, were provided by DOW Electronic Materials. Other chemicals
were purchased from Aldrich, Acros, and VWR and were used without further
purification unless otherwise noted. Prior to use, tetrahydrofuran (THF)
was distilled over sodium and stored under N2. Dichloromethane
(CH2Cl2) was distilled over calcium hydride and stored under
nitrogen.

[0084] The instruments used for the analysis of the precursors and the
products are detailed as follows: 1H and 13C NMR spectra were
recorded on a Varian 500 MHz spectrometer interfaced to a UNIX computer
using Mercury software. Chemical shifts were referred to the solvent
proton resonance. IR spectra were recorded on an IR Prestige 21 system
(Shimadzu Corp.) and analyzed by using the IR solution software.

[0085] The polymer molecular weight and molecular weight distribution were
determined by Gel Permeation Chromatography (GPC). The GPC was conducted
on a Waters 1515 HPLC (Waters Chromatography, Inc.) equipped with a
Waters 2414 differential refractometer, a PD2020 dual-angle (15°
and 90°) light scattering detector (Precision Detectors, Inc.),
and a three-column series (PL gel 5 micrometer (μm) Mixed C, 500
Angstroms (Å), and 104 Å, 300×7.5 millimeters (mm)
columns; Polymer Laboratories, Inc.). The system was equilibrated at
40° C. in THF, which served as the polymer solvent and eluent with
a flow rate of 1.0 milliliters per minute (mL/min). Polymer solutions
were prepared at a known concentration (3-5 milligrams per milliliter
(mg/mL)) and an injection volume of 200 microliters (μL) was used.
Data collection and analysis were performed with Precision Acquire
software and Discovery 32 software (Precision Detectors, Inc.),
respectively. Inter-detector delay volume and the light scattering
detector calibration constant were determined by calibration using a
nearly monodisperse polystyrene standard (Polymer Laboratories,
Mp=90 kiloDaltons (kDa), Mw/Mn<1.04). The differential
refractometer was calibrated with standard polystyrene reference material
(SRM 706 NIST), of a known specific refractive index increment dn/dc
(0.184 milliliters per gram (mL/g)). The dn/dc values of the analyzed
polymers were then determined from the differential refractometer
response.

[0086] The surface energy of the film was calculated using the
Owens-Wendt-Rabel-Kaelble (OWRK) method after measuring the contact angle
with an optical tensiometer (KSV Instruments, Attension Theta). The X-ray
Photoelectron Spectroscopy (XPS) experiments were performed on a Kratos
Axis Ultra XPS system with a monochromatic aluminum X-ray source (10
milliAmperes (mA), 12 kilovolts (kV)). The binding energy scale was
calibrated to 285 electron volts (eV) for the main C1s (carbon 1s) peak.

[0087] The secondary ion mass spectrometry (SIMS) measurements were
carried out with a custom-built SIMS instrument coupled to a
time-of-flight (TOF) mass analyzer. The instrument used in these studies
is equipped with a C60 effusion source capable of producing
C60+2 projectiles with total impact energy of 50 kiloelectron
volts (keV). The SIMS analysis of the polymer samples was conducted in
the superstatic regime, where less than 0.1% of the surface is impacted.
This restriction ensured that each time the surface was impacted by a
primary ion, an unperturbed area of the surface was sampled. The
superstatic measurements were conducted in the event-by-event
bombardment-detection mode, where a single primary ion impacted on the
surface and the secondary ions were collected and analyzed prior to
subsequent primary ions impacting the surface. All secondary ions
detected in a single impact originated from a 10 nm radius on the
surface.

[0088] Each polymer sample was measured three times at different locations
on the sample by TOF-SIMS. Each measurement consisted of
˜3×106 projectile impacts on an area ˜100 μm in
radius. Multiple measurements were performed to ensure sample
consistency. A quantitative estimate of surface coverage of fluorine
containing molecules was calculated for each sample by using the signals
at m/z=19, corresponding to fluorine (F) anion, and m/z=191,
corresponding to C8F4H3O anion.

[0089] The EBL was carried out by using JEOL JSM-6460 Scanning Electron
Microscope (SEM) equipped with DEBEN laser stage. The system was operated
at 30 kV accelerating voltage and 10 picoAmperes (pA) beam current with
series of exposure dosage ranging from 200 to 600 μC/cm2
(corresponding to 6 to 18 millijoules per square centimeters
(mJ/cm2)). A 5×5 μm pattern with features including varied
line width, i.e., 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 nm,
respectively, and fixed 500 nm space was designed and used to evaluate
the lithographic behavior of polymer resists.

[0091] Synthesis of the first polymer--(NB-P(TFpHS)12). This example
was conducted to demonstrate the manufacturing of the first polymer. The
nomenclature employed here is as follows: NB--norbornene with the chain
transfer agent; TF--tetrafluoro; pHS--para-hydroxystyrene;
P(TFpHS)12)--poly(tetrafluoro-para-hydroxystyrene) having 12 repeat
units.

[0093] This example was conducted to demonstrate the manufacturing of
another first polymer.

[0094] Synthesis of the first polymer--(NB-P(TFpHS)10). The
nomenclature employed here is as follows: NB--norbornene with the chain
transfer agent; TF--tetrafluoro; pHS--para-hydroxystyrene;
P(TFpHS)10)--poly(tetrafluoro-para-hydroxystyrene) having 10 repeat
units.

[0095] The first polymer was manufactured as follows. To a 25 mL Schlenk
flask equipped with a magnetic stirring bar dried with flame under
N2 atmosphere, was added NB-CTA (510 mg, 1.32 mmol), TFpHS (5.06 g,
26.4 mmol), AIBN (12.9 mg, 79.2 μmol), and 12 mL of 2-butanone. The
mixture was stirred 10 minutes at room temperature and degassed through
five cycles of freeze-pump-thaw. After the last cycle, the reaction
mixture was stirred 10 minutes at rt and immersed into a pre-heated oil
bath at 65° C. to start the copolymerization. After 11 h, the
polymerization was quenched by cooling the reaction flask with liquid
N2. The copolymer was purified by precipitation into 300 mL of
hexane twice. The pink oil was collected through centrifugation, washed
with 300 mL of hexane, and kept under vacuum overnight for removing
residual solvents. Yield 1.7 g of product, 61% yield based upon
˜45% monomer conversion. Mn,GPC=2,450 Da (laser detector),
PDI=1.08. The 1H NMR, 13C NMR and IR spectra were similar as
that obtained from the first polymer. The glass transition temperature
(Tg)=150° C.

Example 3

[0096] Synthesis of the second polymer--(NB-P(pHS13-co-PhMI13)).
This example was conducted to demonstrate the manufacturing of the second
polymer. The nomenclature employed here is as follows: NB--norbornene
with the chain transfer agent; pHS--para-hydroxystyrene; PhMI--N-phenyl
maleimide; P(pHS13-co-PhMI13)--poly(para-hydroxy
styrene-co-N-phenyl maleimide) where the para-hydroxy styrene is
polymerized having 13 repeat units and the N-phenyl maleimide is
polymerized to the poly(para-hydroxy styrene) and has 13 repeat units
too.

[0098] Synthesis of the second polymer--(NB-P(pHS8-co-PhMI8)).
This example was also conducted to demonstrate the manufacturing of the
second polymer. The nomenclature employed here is as follows:
NB--norbornene with the chain transfer agent; pHS--para-hydroxystyrene;
PhMI--N-phenyl maleimide; P(pHS8-co-PhMI8)-- poly(para-hydroxy
styrene-co-N-phenyl maleimide) where the para-hydroxy styrene is
polymerized having 8 repeat units and the N-phenyl maleimide is
polymerized to the poly(para-hydroxy styrene) and has 8 repeat units too.

[0099] The second polymer was manufactured as follows. To a 50 mL Schlenk
flask equipped with a magnetic stirring bar dried with flame under
N2 atmosphere, was added NB-CTA (802 mg, 2.08 mmol), pHS (2.50 g,
20.8 mmol), PhMI (3.60 g, 20.8 mmol), AIBN (16.9 mg, 104 μmol) and 20
mL of anhydrous 1,4-dioxane. The mixture was stirred 10 minutes at RT and
degassed through four cycles of freeze-pump-thaw. After the last cycle,
the reaction mixture was stirred 15 minutes at RT and immersed into a
pre-heated oil bath at 65° C. to start the copolymerization. After
4.5 hours, the polymerization was quenched by cooling the reaction flask
with liquid N2. The copolymer was purified by precipitation into 600
mL of diethyl ether twice. The pink precipitate was collected through
centrifugation, washed with 400 mL of diethyl ether and 400 mL of hexane,
and kept under vacuum overnight for removing residual solvents. Yield 2.8
g of product, 73% yield based upon ˜60% conversion for both
monomers. Mn,GPC=2,730 Da (RI detector), Mn,GPC=3,800 Da (laser
detector), PDI=1.12. The 1H NMR, 13C NMR and IR spectra were
similar to that measured in the Example 3. The glass transition
temperature (Tg)=130° C.

Example 5

Synthesis of Brush I

[0100] This example was conducted to demonstrate the manufacturing of a
brush (the graft block copolymer) having the structure
((PNB-g-PTFpHS12)3-b-(PNB-g-P(pHS13-co-PhMI13)26-
). The nomenclature adopted here is as follows: PNB--polynorbornene, which
is the backbone polymer; PTFpHS12--poly(tetrafluoro-para-hydroxy
styrene) having 12 repeat units; P(pHS13-co-PhMI13)--is the
same as in Example 3. The
((PNB-g-PTFpHS12)3-b-(PNB-g-P(pHS13-co-PhMI13)26-
) is therefore a copolymer comprising a first block having a
polynorbornene backbone of 3 repeat units onto which is grafted the
poly(tetrafluoro-para-hydroxy styrene) (the first polymer) having 12
repeat units and a second block having a polynorbornene backbone of 26
repeat units onto which is grafted the copolymer (the second polymer)
comprising 13 repeat units of poly(parahydroxystyrene) and 13 repeat
units of poly(N-phenyl maleimide).

[0102] This example was also conducted to demonstrate the manufacturing of
a brush having the structure
((PNB-g-PTFpHS10)4-b-(PNB-g-P(pHS8-co-PhMI8)37).
The nomenclature adopted here is as follows: PNB--polynorbornene, which
is the backbone polymer; PTFpHS10--poly(tetrafluoro-para-hydroxy
styrene) having 10 repeat units; P(pHS8-co-PhMI8)--is the same
as in Example 4. The
((PNB-g-PTFpHS10)4-b-(PNB-g-P(pHS8-co-PhMI8)37)
is therefore a copolymer comprising a first block having a polynorbornene
backbone of 4 repeat units onto which is grafted the
poly(tetrafluoro-para-hydroxy styrene) (the first polymer) having 10
repeat units and a second block having a polynorbornene backbone of 37
repeat units onto which is grafted the copolymer (the second polymer)
comprising 8 repeat units of poly(parahydroxystyrene) and 8 repeat units
of poly(N-phenyl maleimide).

[0103] The nomenclature adopted in this example is the same as that
adopted in the Example 5. To a 10 mL Schlenk flask equipped with a
magnetic stirring bar dried with flame under N2 atmosphere, was
added the modified Grubbs catalyst (5.25 mg, 7.21 μmol) and 0.45 mL of
anhydrous CH2Cl2. The modified Grubbs catalyst is shown in the
formula (4) above.

[0104] The reaction mixture was stirred for 1 minute at RT to obtain a
homogeneous solution and degassed through three cycles of
freeze-pump-thaw. After the last cycle, the solution of Example 2 (69.7
mg, 30.3 μmol) in 0.65 mL of anhydrous THF (degassed through three
cycles of freeze-pump-thaw) was quickly added with an airtight syringe.
The reaction mixture was allowed to stir for 40 minutes at RT before
adding the solution of Example 4 (550 mg, 201 μmol) in 5.0 mL of
anhydrous THF (degassed through three cycles of freeze-pump-thaw) with an
airtight syringe. The reaction mixture was stirred for 3 hours at RT
before quenching the polymerization by adding 0.5 mL of ethyl vinyl ether
(EVE), and was further stirred for 1 hour at RT. The solution was
precipitated into 90 mL of diethyl ether. The precipitate was collected
through centrifugation and re-dissolved into 20 mL of acetone. The
solution was then precipitated into 200 mL of diethyl ether. The
precipitate was collected through centrifugation, washed with 200 mL of
diethyl ether and 200 mL of hexane, and kept under vacuum overnight for
removing residual solvents. Yield 550 mg of product, 94% yield based upon
˜90% conversion for Example 2 and ˜95% conversion for Example
4, respectively. Mn,GPC=152 kDa (laser detector), PDI=1.26. The
1H NMR, 13C NMR and IR spectra were similar as that for Example
5. The glass transition temperatures were 130 and 150° C.,
respectively.

Example 7

[0105] This example demonstrates the manufacturing of a control sample
that does not contain a block that has a surface energy reducing moiety.
The control sample has the formula
((PNB-g-P(pHS13-co-PhMI13)24) and comprises a backbone
that contains a backbone polymer of polynorbornene having 24 repeat units
with a copolymer comprising 13 repeat units of poly(parahydroxystyrene)
and 13 repeat units of poly(N-phenyl maleimide). The polymer forms a
brush that does not display the same degree of self-assembly as the brush
that contains the fluorine atom (the fluorine atom being an example of
the surface energy reducing moiety).

[0107] This example was conducted to demonstrate the manufacturing of a
polymer thin film from the brushes of Example 5 (brush I), 6 (brush II)
or 7 (brush control). The solution of respective polymer in cyclohexanone
(1.0 wt %) was prepared and passed through a PTFE syringe filter (220 nm
pore size) before using. The solution was applied onto a UV-O3
pre-treated silicon wafer (the amount of applied polymer solution should
be sufficient to cover the whole wafer surface) and spin coated at 500
revolutions per minute (rpm) for 5 seconds (s), followed by spinning at
3,000 rpm for 30 seconds (200 rpm/s acceleration rate for each step) to
afford respective thin films with thicknesses of 18 to 25 nm.

[0108] The polymer film-coated silicon wafer was kept in a desiccator
filled with saturated acetone atmosphere under vacuum for 20 hours. After
the annealing process, the excess solvent was removed by pumping under
vacuum and the N2 gas was slowly backfilled to open the desiccator.

[0109] The respective films were then characterized by tapping-mode atomic
force microscopy (AFM). The 25 nm-thick film from the control sample
(Example 7) showed noticeable phase segregation. The FIG. 3 depicts
photomicrographs of these samples. The FIG. 3A show the brush control
suggests the formation of cylindrical assemblies. However, these
assemblies showed low degrees of order and relatively large sizes (>50
nm, estimated from the inserted imaging in the FIG. 3A).

[0110] By comparison, the films from brush I (Example 5) and II (Example
6) exhibited sufficiently homogeneous surface topology (FIGS. 3B and 3C,
respectively) with root mean square (RMS) roughness less than 0.2 nm. The
film thickness, as measured by AFM, was 18±2 nm and 22±2 nm for
brush I and II, respectively, which showed agreement with the PNB
backbone contour length of each brush precursor (17.4 and 24.6 nm for
brush I and II, respectively). Therefore, the tunability of the radial
dimension of molecular brush could provide a feasible approach for
manipulating the film thickness and therefore a parameter for determining
pattern features in direct writing lithographic processes.

[0111] The surface topographical homogeneities and the approximately
monomolecular layer thicknesses of the brush films suggest that the brush
polymer components within the films prefer to adopt perpendicular
orientations to the wafer surface. Without being limited to theory, the
vertical alignment can be attributed to the intrinsically cylindrical
topology of brush polymers, which is induced by the strong size-exclusion
effects between covalently-tethered dense polymer grafts. The fluorinated
block segments in the unique graft block copolymers are believed to
contribute effects to promote and assist in achieving vertical alignment,
due to their preferential surface migration driven by their relatively
lower surface energy.

Example 9

[0112] This example was conducted to demonstrate the manufacturing of a
polymer thin film from compositions that contain the brushes of Example 5
(brush I), 6 (brush II) or 7 (brush control) and to demonstrate the
crosslinking of the film as well as the preparing of a negative tone
photoresist (by either exposing portions of the film to UV light or to an
electron beam).

[0113] Triphenylsulfonium hexafluoroantimonate was used as photoacid
generator (PAG) and
N,N,N',N',N'',N''-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-triamine
(HMMM) was selected as both multivalent cross-linker and acid quencher.
The solution of polymer:HMMM:PAG was mixed in a weight ratio of
0.75:0.15:0.10 wt % in cyclohexanone was prepared and passed through a
PTFE syringe filter (220 nm pore size) before casting the film as
detailed in the Example 8. The solution was applied onto UV-O3
pre-treated silicon wafer (the amount of applied solution should be
sufficient to cover the whole wafer surface) and spin coated at 500 rpm
for 5 seconds, followed by spinning at 3,000 rpm for 30 seconds (200
rpm/s acceleration rate for each step) to afford thin films with
thicknesses of 25 to 28 nm.

[0114] The polymer resist film-coated wafer was exposed to the UV light
source (254 nm, 6 W) via a quartz photomask at a distance of about 20 cm
for 2 minutes. After exposure, the exposed film was post-baked on a
120° C. hotplate for 1 minute and then the unexposed area was
developed by dipping the wafer into 0.26 M tetramethylammonium hydroxide
(TMAH) aqueous solution for 30 seconds, followed by rinsing with DI water
and drying with N2 flow.

[0115] The films were alternatively exposed to electron beam "writing"
with a predesigned pattern, the exposed wafer was post-baked on a
90° C. hotplate for 1 minute and dipped into 0.26 M TMAH.sub.(aq)
solution for 1 minute. The wafers were rinsed with DI water and dried by
N2 flow.

[0116] The thin film was characterized by tapping-mode atomic force
microscopy (AFM). The results are shown in the photomicrograph in the
FIG. 3. The 25 nm-thick film from the brush control showed noticeable
phase segregation (phase image in FIG. 3A), which suggested the formation
of cylindrical assemblies. However, these assemblies showed low degrees
of order and relatively large sizes (>50 nm, estimated from the
inserted imaging in the FIG. 3A). By comparison, the films from brush I
and II exhibited sufficiently homogeneous surface topography (FIGS. 3B
and 3C respectively) with RMS roughness of less than 0.2 nm. The film
thickness, as measured by AFM, was 18±2 nm and 22±2 nm for brush I
and II respectively, which showed agreement with the polynorbornene
backbone contour length of each brush precursor (17.4 and 24.6 nm for 1
and II respectively).

[0117] The surface topographical homogeneities and the approximately
monomolecular layer thicknesses of the brush films suggest that the brush
polymer components within the films preferred to adopt perpendicular
orientations to the wafer surface. The vertical alignments could be
attributed to the intrinsically cylindrical topology of brush polymers,
which is induced by the strong size-exclusion effects between
covalently-bonded polymers that are grafted onto the backbone polymers.
Meanwhile, the fluorinated block segments in the graft block copolymers
would contribute effects to promote and assist the vertical alignments,
due to their preferential surface migration driven by their relatively
lower surface energies.

Example 10

[0118] This example was conducted to ascertain the performance of the
graft block copolymer in a lithographic application as a chemically
amplified resist. After exposure to the electromagnetic radiation
described in the Example 9, the samples were subjected to post baking,
which is detailed below. Triphenylsulfonium hexafluoroantimonate was used
as photoacid generator (PAG) and N,N,N',N',
N'',N''-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-triamine (HMMM) was
selected as both multivalent cross-linker and acid quencher. Example 9
details the manufacturing of the resist. Atomic force micrograph (AFM)
images of the respective brushes is shown in the FIG. 4.

[0119] From the AFM topographic images of the resulting patterns, brush I
(FIG. 4A) displays a better lithographic performance than brush II (FIG.
4B), as evidenced by noticeably less line-edge roughness (LER) and less
line-broadening effects. Cross-linked polymer residue was present within
the pattern developed areas for brush II resists, which indicated that
brush II CAR has a higher sensitivity than a brush I CAR. Although both
brush-based CARs did not exhibit advantages over the brush control-based
CAR (FIG. 4C) in the micro-scale 254 nm photolithographic survey, the
electron beam lithography (EBL) of the brush resists revealed their
significant superiorities over the brush control counterpart in the
high-resolution nanoscopic pattern formation. Direct-EBL is an EBL
process without post-exposure baking (PEB). This is the advantage of
using bottle-brushes, i.e., it allows for the use of direct EBL.

[0120] The post-exposure baking EBL (PEB-EBL) studies of brush I, II and
the brush control-based CARs (CAR-I, CAR-II, and CAR-LC, respectively)
were carried out by applying the similar resist formulations as used for
UV-photolithography (detailed above), while using the triphenylsulfonium
perfluoro-1-butanesulfonate as PAG. A designed pattern with line width
ranging from 10 to 100 nm features was used to evaluate their
lithographic performances, through measuring the height and width of each
resulting line at two exposure dosages (250 and 400 μC/cm2,
corresponding to a EUV (13.5 nm) dose of approximately 7.5 and 12
mJ/cm2, respectively) by AFM. As shown in FIGS. 2A-2D, both CAR-I
and CAR-II could create patterns with full line integrities at each
exposure dosage. By comparison, the patterns from CAR-BC (brush control)
only had rational features for the 50 to 100 nm designed lines (FIG. 2F),
even at the relatively higher dosage (400 μC/cm2). Furthermore,
the parameters of the patterned lines in FIG. 2F were indeed not
qualified for practical purpose (data not shown).

[0121] For the brush CARs in this study, the line features of the latent
30 nm to 100 nm lines were satisfactory, especially for the CAR-II after
400 μC/cm2 exposure (FIG. 2E). We speculated that the better
latent line-width features of CAR-II were induced by the intrinsic
geometric factor of brush II. Although both I and II have cylindrical
morphologies, the relatively shorter grafts in II render it a "thinner"
column by reducing the chain entanglements after vertically aligning on
the substrate surface. Currently, an about 30-nm isolated line was
obtained for CAR-II under the aforementioned conditions. It can therefore
be concluded that the brush molecular lengthwise and widthwise
dimensional tuning, which can be easily achieved by the current
"grafting-through" synthetic strategy, plays a critical role on the
lithographic performance and eventually, that molecular pixels could be
realized through further systematic optimizations of brush backbone and
graft lengths, together with chemical compositions.

Patent applications by Guorong Sun, Bryan, TX US

Patent applications by James W. Thackeray, Braintree, MA US

Patent applications by Karen L. Wooley, College Station, TX US

Patent applications by Peter Trefonas, Iii, Medway, MA US

Patent applications by Sangho Cho, Bryan, TX US

Patent applications in class Ethylenic unsaturation within the side chain component

Patent applications in all subclasses Ethylenic unsaturation within the side chain component